The present invention concerns a method of utilizing biomass from agricultural crop essentially in its naturally moist state, as well as a screw press to carry out said method.
Examples of biomass from agricultural crop in its essentially naturally moist state that can be taken into consideration are plants or parts of plants with especially high protein content and/or sugar content, their derivatives and residues. This applies in particular to clover, alfalfa and grass, but also to bean plants, soybean, sorghum, mustard, collard greens, turnips, banana leaves, bagass, grape skins, husks/skins, residue of fruit such as residue of citrus fruits and pitted fruit, and also rampant water plants such as duck-weed and water hyacinth, and several others of that nature. In connection with the use of biomass, individual steps like shredding, extruding, hydrolysis, cooling, decomposition by enzymes, decomposition by microorganisms, anaerobic decomposition, recovery of fermentation gases, discharge of various phases essentially like fluid phases, phases of low solids content, phases of high solids content, or gas-type phases etc., are already known per se, as well as the individual utilization of separated phases as a feed, a fertilizer, for the production of ethanol, for the production of carbon dioxide, as a fuel, etc. In screw presses it is also known to form sealing plugs of the treated material for the purpose of separating various chamber areas from one another.
However, this prior art is not known as a whole in the form of a single integrated system. In detail this means:
WO-82/01483 discloses a method of utilizing of a mixture of organic and inorganic material in municipal waste, as well as a device for the continuous operation of this method. The material is provided in chopped form; then follows a sterilization treatment of the entire waste material by means of pressurized vapor; subsequently the pressure is released and the vapor-treated waste material is separated into a phase of high organic materials content that is capable of flowing and a phase of high inorganic solids content; then follows a decomposition of organic materials in the phase capable of flowing, by the action of enzymes and/or by fermentation through microorganisms, and the decomposed phase is separated into solids and fluid; the fluid is distilled and the residue is again separated into solids and fluid; the latterfluid is fermented under anaerobic conditions and the gas phase that develops during this process is separated in view of being utilized; the fluid from the fermentation and the solids in the residue of the distillation are also utilized.
With this method according to WO-82/01483, the waste material is only subjected to pressure, however, it will not be simultaneously compressed (pressed and compacted) and hence, it remains voluminous and maintains its moisture.
Also, the separation of organic and inorganic contents takes place only after the pressure treatment.
In addition, there is an irreversible expansion of the vapor phase after which the energy of the vapor cannot be recovered and recycled to the process because it is lost in the condensed water.
Moreover, a very first method step is the sterilization of the material in its still voluminous loose shape, which may be appropriate when the method is applied to municipal waste, since such waste endangers the environment. To apply this method to biomass from agricultural crop is not optimal, since such biomass does not endanger the environment and therefore it is not urgent to sterilize it while in its still voluminous state. However, the sterilization cannot be delayed when the method of WO-82/01483 is performed, since it takes place spontaneously together with the pressurized vapor treatment as a step that imperatively occurs prior to the release of pressure.
In general the method according to WO-82/01483 is directed to first separate the organic and inorganic materials contents and only then initiate their utilization, whereas such separation is not appropriate at all to biomass from agricultural crops.
Thus, the method according to WO-82/01483 is not capable of providing economically optimal results with biomass from agricultural crop essentially in its naturally moist state.
DE-4423099 discloses a method of utilizing biomass from agricultural crop as well as a screw press to perform the method. The chopped biomass is compressed in a screw press and separated into a phase of low solids content and a phase of high solids content; the phase of low solids content is separated; then a fermentation is performed that is not described any further. This method is suited for the production of fermentation gas, however, it is not suitable for the production of high-grade products like ethanol, protein concentrate and fibers. There takes place no vapor treatment nor expansion nor cooling of the starting material.
U.S. Pat. No. 4,302,543 discloses a method of utilizing biomass from agricultural crop. The chopped biomass is compressed in an extruder under high pressure and high temperature without any prior separation of solids and fluid; after sufficient cooling, the substance is hydrolyzed by the action of enzymes. This method was developed for the utilization of raw materials having a high content of starch such as corn, wheat, rice, barley, rye and oats, however, it does not allow for the processing of raw materials that primarily contain cellulose, for the production of ethanol, protein concentrate and fibers. Also, there takes place no compression of the material to separate solids and fluid and no recovery of vapor at the end of the heat treatment. A release of the pressure applied to the material kept at high temperature and under high pressure is said in the description to be known prior art.
U.S. Pat. No. 4,842,877 discloses an essentially chemical method for the processing of biomass from agricultural crop by the decomposition of wood fibers (lignocellulose) to become a feed supplement. The first step of this method is an alkaline hydrolysis at somewhat elevated temperature. The fluid phase obtained is mixed with a chelating agent. Among other chemical method steps an oxidation with hydrogen peroxide and oxygen takes place in an extruder.
JP-58-014995 (as can be read in Patent Abstracts of Japan) discloses the improvement of a fermentation method by means of prior removal of ballast fibers that are not capable of fermentation. The material to be fermented is compressed in a screw press and simultaneously separated into two phases; the phase of high solids content is separated; then the phase of low solids content is fermented, the fermentation gas that develops during this process is separated and utilized, the remaining mixture phase that is capable of flowing is in its turn separated into two phases, and both phases will be utilized. There is no vapor treatment, no cooling and no addition of enzymes and/or yeast that would be required for the production of ethanol and by-products.
DE-2919518 discloses a method of utilizing biomass from agricultural crop essentially in its naturally moist state, as well as a screw press to carry out said method. The chopped biomass is treated with pressurized vapor; after cooling down, a fermentation with microorganisms takes place, optionally with addition of yeast, and only then a separation of the mixture into two phases takes place in the screw press and these phases are processed. This method was developed to obtain ethanol from free sugar contained in sugar cane and is not suitable to produce ethanol from cellulose. In addition, no enzymes are used for the cleavage of the fibers contained in the raw materials.
U.S. Pat. No. 4,321,328 discloses a method for the recycling of ethanol containing liquor, which may be applied to the production of ethanol from raw materials containing cellulose. In this method the raw material is suspended by means of recycled ethanol containing liquor and then mechanically disintegrated, hydrolyzed by the action of enzymes and fermented with microorganisms. Seizure, conditioning and pre-treatment of the raw materials are not further described.
EP-0005703 discloses a method for the utilization of solid household waste and biomass. In the case of processing household waste, various substances contained therein are first separated from one another in several steps. Then, all raw materials are subjected to a grinding of the contained substances that are capable of being hydrolyzed, a sterilization and a saccharification by means of sulfurous acid, a neutralization, a fermentation, a separation of the solids and fluid, and a distillation of the fluid phase.
EP-0213023 discloses a method of producing ethanol and gluten from grain.
FR-2550550 discloses a method for the processing of biomass from agricultural crop. The first step of this method is a hydrolysis at high temperature and under high pressure; this is followed by a release of pressure in the course of which the material is separated into a fluid phase and a solid phase; the lignin is removed from the solid phase by means of a solvent; then, a hydrolysis again takes place at high temperature and under high-pressure; if necessary, a saccharification by the action of enzymes will follow. The object of this method is the liquefaction and separation of hemicellulose, cellulose and lignin.
DE-3715953 discloses a method for the processing of materials containing cellulose such as waste containing paper, straw and wood waste, as well as a screw press for performing the method. Following the chopping of the mass, a dissolution and a sterilization take place in the screw press through an increase in temperature and pressure, then a completion step follows in a closed system with a discharge of oxygen, and the product thereof is then further processed. There is no treatment of the raw materials with vapor.
The aforementioned prior art does not lead to any obvious combination of prior art techniques that would allow to avoid the aforementioned disadvantages that arise when the method of WO-82/01483 is performed.
More particularly, using this prior art did not allow up to now to obtain any economically acceptable implementation of the separate method steps into an optimally operated integrated system. This could be attributed to several reasons:
Where raw materials containing sugar or starch are processed, the cost of the raw materials in comparison to the price for ethanol is in general too high. PA1 Where methane gas (fermentation gas) is produced the low price of the product merely allows to apply the method to raw materials, the disposal of which is compulsory. On the other hand, economical utilization of raw materials from agricultural crops is not possible. PA1 Where ethanol is produced exclusively, the benefits are too low, compared to the expensive processing of a high-tech method. This supports the economic pressure to establish installations with a very large processing capacity. High development costs, as well as high transportation costs for raw materials, must be included in the calculation for such large installations. PA1 Utilization of various substances contained in the biomass; PA1 Linking, within the method itself, the requirements regarding the treatment and storage of raw materials with the requirements regarding the utilization of the contained substances; PA1 Optimal further processing and utilization of the separated essentially fluid or solid phases; and PA1 Optimizing the overall energy balance of not only the individual method steps but of the method as a whole. PA1 (a) Providing the biomass in a chopped form appropriate to processing in screw presses; PA1 (b) Pressing the provided biomass from method step (a) and concomitant separation of the pressed biomass into each of a phase of low solids content and a phase of high solids content, and separation of the phase of low solids content for the latter's utilization; PA1 (c) Processing the phase of high solids content from method step (b) with pressurized vapor; PA1 (d) Releasing pressure of the pressurization built-up at method step (c) and concomitant separation of the vapor-treated phase from method step (c) into each of a vapor phase and a phase of high solids content, and separation of the vapor phase for the latter's utilization; PA1 (e) Cooling the phase of high solids content from method step (d) and concomitant utilization of heat recovered in this step; PA1 (f) Decomposition of materials in the cooled phase from method step (d) by the action of enzymes and/or by fermentation with microorganisms and concomitant separation of the decomposed phase into each of a gaseous phase and a phase capable of flowing, and separation of the gaseous phase for the latter's utilization; PA1 (g) Separation of the phase capable of flowing from method step (f) into each of a phase of low solids content and a phase of high solids content, and separation of the phase of high solids content for the latter's utilization; PA1 (h) Utilization of the phase of low solids content from at least one of the method steps (b) and (g).